Conventionally, an industrial robot for carrying a work-piece such as a semiconductor wafer has been known which is structured of a base, a link mechanism, an arm part and a hand part (see, for example, Patent Literature 1). In the industrial robot described in Patent Literature 1, the link mechanism is provided with a base side link part which is turnably attached to the base and an arm side link part which is turnably attached to the base side link part.
The base side link part is turnably held by a link mechanism motor which is incorporated into the base. Further, the base side link part is incorporated with a base side pulley which is fixed to the base, an arm part side pulley which is fixed to the arm side link part, and a belt which is stretched over the base side pulley and the arm part side pulley. The base side pulley and the arm part side pulley of the industrial robot are formed so that the ratio of their diameters is set to be 2:1 and, when the link mechanism motor is rotated, a tip end side of the arm side link part performs a linear operation.
Further, in the industrial robot, the arm part is turnably attached to a tip end side of the arm side link part. The arm part is connected with an arm part motor which is incorporated into the arm side link part. The arm part motor is incorporated into the arm side link part with an upper and lower direction as a direction of its turning shaft.
[PTL 1] Japanese Patent Laid-Open No. 2007-152490
In the industrial robot described in Patent Literature 1, the ratio of the diameter of the base side pulley to the diameter of the arm part side pulley is set to be 2:1. Further, loads of the arm side link part, the arm part and the hand part are applied to the belt which is stretched over the base side pulley and the arm part side pulley. Therefore, the sizes of the base side pulley, the arm part side pulley and the belt which are disposed in the inside of the base side link part tend to be increased. Accordingly, in the industrial robot, the size of the base side link part tends to be increased and, as a result, the industrial robot tends to be enlarged.
Further, in the industrial robot, the arm part motor is incorporated into the arm side link part with the upper and lower direction as a direction of its turning shaft and thus the thickness of the arm side link part is increased. Therefore, in the industrial robot, the height of the hand part tends to be increased and the minimum height (pass line) that the robot is accessible may be increased.